The Relationship of Exhaled Nitric Oxide Levels with Measures of Disease Control and Disease Severity in Asthma

Abstract

The current concept of asthma pathogenesis is that a characteristic chronic inflammatory process involving the airway wall causes the development of airflow limitation and increased airway responsiveness. Exhaled NO is significantly greater in asthmatic subjects than in normal subjects. Recently, the measurement of exhaled nitric oxide has been proposed as a noninvasive means for assessing the degree of airway inflammation. We examined the correlation between asthma disease control and disease severity and exhaled NO as a marker of airway inflammation. In this cross-sectional study, we chose the use of rescue medications and the degree of reversibility of airflow obstruction after administration of a bronchodilator as measures of asthma control. We chose irreversible airflow obstruction, and baseline predicted FEV1 as measures of asthma severity. We designed a questionnaire for the 86 patients (ages ranging from 9 to 92 years) with asthma, performed spirometric testing before and after administration of a bronchodilator, and measured exhaled NO levels in all participants. Exhaled NO levels were not correlated with the markers of asthma disease control: daily use of rescue medications (p=0.381) and reversibility of airflow obstruction (p=0.506). Exhaled NO levels were not correlated with the markers of asthma disease severity: fixed airflow obstruction (p=0.842) and severity, according to predicted FEV1 (p=0.820). We conclude that exhaled NO did not correlate with measures of asthma control and severity in this study. A study with a larger sample size may demonstrate statistical significance. A longitudinal assessment of exhaled NO levels may provide a clinical role for NO in monitoring asthma control and severity.